1. Field of the Invention
The present invention relates generally to apparatus and methods for the endoluminal placement of resilient tubular prostheses, such as grafts, stents, stent-grafts, and other structures. More particularly, the present invention relates to a delivery catheter for the placing of such intraluminal tubular protheses in body lumens, including blood vessels, for the treatment of abdominal and other aneurysms.
Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease and/or genetic predisposition which can weaken the arterial wall and allow it to expand. While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries, with the majority of aortic aneurysms occurring in the abdominal aorta, usually beginning below the renal arteries and often extending distally into one or both of the iliac arteries.
Aortic aneurysms are most commonly treated in open surgical procedures where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered to be an effective surgical technique, particularly considering the alternative of a usually fatal ruptured abdominal aortic aneurysm, conventional vascular graft surgery suffers from a number of disadvantages. The surgical procedure is complex and requires experienced surgeons and well equipped surgical facilities. Even with the best surgeons and equipment, however, patients being treated frequently are elderly and weakened from cardiovascular and other diseases, reducing the number of eligible patients. Even for eligible patients prior to rupture, conventional aneurysm repair has a relatively high mortality rate, usually from 3% to 10%. Morbidity related to the conventional surgery includes myocardial infarction, renal failure, impotence, paralysis, and other conditions. Additionally, even with successful surgery, recovery takes several weeks, and often requires a lengthy hospital stay.
In order to overcome some or all of these drawbacks, endovascular graft placement for the treatment of aneurysms has been proposed. Although very promising, many of the proposed methods and apparatus suffer from other problems. In particular, delivery and placement of the endovascular graft within the vasculature can be problematic. Proper positioning and sizing of the endovascular graft is critical to the successful treatment of an aneurysm. Grafts are often resilient, biased to expand and anchor the graft within the body lumen. These resiliently expanding grafts are tightly compressed within the catheter and impose significant forces against the surrounding catheter bodies, often leading to excess friction between the graft and the catheter wall. These forces complicate the loading of the graft into the catheter, as well as the accurate release of grafts and stents in body lumens. Moreover, the catheters must maneuver the graft within the vascular system. Thus, the catheters are required to have flexible, elongate bodies which are particularly susceptible to the expanding graft, often resulting in invagination of the graft in the soft material of the catheter wall.
For these reasons, it would be desirable to provide improved apparatus and methods for endovascular placement of intraluminal protheses, including grafts, stents, and stent-grafts, for treating aneurysms and other conditions. It would be particularly desirable to provide delivery catheters and methods for the placement of endoluminal tubular prostheses which would facilitate the controlled release of resilient tubular prostheses. It would be particularly desirable to provide delivery catheters and methods which reduce the frictional forces created by the resilient expansion against the catheter during loading and release of the prostheses.
2. Description of the Background Art
Vascular grafts and devices for their endoluminal placement are described in U.S. Pat. Nos. 5,282,824; 5,272,971; 5,242,399; 5,219,355; 5,211,658; 5,201,757; 5,192,297; 5,190,058; 5,158,548; 5,147,370; 5,104,399; 5,092,877; 5,078,726; 5,019,085; 4,990,151; 4,950,227; 4,913,141; 4,886,062; 4,820,298; 4,787,899; 4,617,932; 4,562,596; 4,577,631; and 4,140,126; and European Pat. Publications 539,237; 533,511; 518,839; 518,704; 508 473; 505,686; 466 518; and 461 791. Catheters for placing vascular stents are described in U.S. Pat. Nos. 5,192,297; 5,092,877; 5,089,005; 5,037,427; 4,969,890; and 4,886,062. Catheters carding a graft structure in a tube or capsule are described in U.S. Pat. Nos. 5,275,622; 5,104,399; and 4,787,899; and EP466518.
The present invention provides apparatus and methods for the endoluminal placement of intraluminal prostheses, including grafts, stents, and stent-grafts, for the treatment of disease conditions, particularly aneurysms. The intraluminal prostheses will typically comprise a resilient, radially compressible, tubular frame having a proximal end, a distal end, and an axial lumen therebetween. In the case of graft prostheses, a liner, typically a fabric, polymeric sheet, membrane, or the like, will line all or most of the luminal surface of the tubular frame, usually extending from a near-proximal location to a near-distal location. Suitable graft structures for placement using the catheters and methods of the present invention are described in copending application Ser. No. 08/255,681, the full disclosure of which is incorporated herein by reference.
The intraluminal prostheses of the present invention are suitable for a wide variety of therapeutic uses, including stenting of the ureter, urethra, biliary tract, and the like. The present devices and methods will also be useful for the creation of temporary or long term lumens, such as the formation of fistulas. The present invention will find its greatest use, however, in the placement of endovascular prostheses into blood vessels for the treatment of abdominal and other aneurysms, vascular stenoses, and the like.
According to the present invention, a delivery catheter for positioning a radially compressible prosthesis comprises an elongate flexible shaft structure having a proximal end and a distal end. The shaft structure includes a prosthesis receptacle near the distal end. A tubular cover is slidably disposed about the shaft with at least one runner disposed within the distal end of the cover, wherein the runner is formed of a harder material than is the cover. The prosthesis can slide against the hard runner material within the cover in response to a distal force applied from the shaft. Advantageously, the hardness of the runner material avoids invagination of the compressed prosthesis frame in the cover while allowing use of a softer, more flexible cover material to facilitate intraluminal maneuvering of the catheter. Additionally, reduced friction between the prosthesis and cover also facilitates the precise positioning of the prosthesis by reducing the forces input at the proximal end and transmitted through the catheter body. The reduced friction of the present delivery catheter is also beneficial when it is necessary to recapture a partially deployed prothesis.
As used herein, a xe2x80x9cprosthesis receptaclexe2x80x9d is a structure or region along a shaft in or over which a radially compressible tubular prosthesis is carried during maneuvering of the shaft and prosthesis within a body lumen. The prosthesis receptacle may include a structure or portion at or near the distal end of the shaft which engages the prosthesis to effect its releasexe2x80x94for example, a distal force imparting structure on the shaft that restrains proximal movement of the prosthesis as the cover slides proximally. Although the devices and methods of the present invention are illustrated with continuous shafts and covers for clarity, the principles of the present invention are fully compatible with an attachable prosthesis cartridge, as described in parent application Ser. No. 08/255,681, previously incorporated by reference. Similarly, catheter diameters may be reduced proximally of the prosthesis to facilitate intravascular maneuvering within the scope of the present invention
Preferably, the present catheter includes a plurality of axially disposed runners affixed together at their proximal ends, thereby reducing contact between the prosthesis and the soft inner surface of the cover. Optionally, the runners remain around the prothesis as the cover slides proximally during deployment. Alternatively, the cover and runners are withdrawn together as the prosthesis slides against the hard runners. Usually, the runners facilitate loading of the prosthesis by compressing the prosthesis as the runners and prosthesis slide together proximally into the cover. The runners are preferably formed of a high strength metal such as stainless steel, a stainless alloy, titanium, a titanium alloy, or a shape memory alloy such as Nitinol(trademark), ideally being 304 or 316 stainless steel.
In a preferred embodiment, the present delivery catheter comprises an elongate flexible shaft and a tubular cover slidably disposed about the shaft. A plurality of elongate runners extend distally from the shaft, the runners having a hardness greater than the cover. The runners are radially constrained when the cover is distally extended over a prosthesis receptacle on the shaft, and are released by proximally retracting the cover. Advantageously, the runners of the present invention can be used to help compress the prosthesis and load it into the cover without damaging the prosthesis frame, either prior to insertion in the patient, or to facilitate recapture of a prosthesis which has been partially deployed within a body lumen.
Preferably, the shaft structure further comprises a core shaft with a guidewire lumen, the core shaft and cover providing an atraumatic distal tip to avoid injury during insertion. Optionally, the core shaft is attached to the shaft. Preferably, the core shaft can slide independently of the shaft, allowing retraction of a distal nosecone through the prosthesis prior to withdrawing the runners. This reduces the possibility of moving a partially deployed prosthesis by allowing manipulation of the nosecone within the prosthesis, rather than withdrawing both the nosecone and the surrounding runners simultaneously.
Optionally, the present catheter further includes a housing at the proximal end of the shaft with a mechanical advantage mechanism, preferably a linear screw, which further reduces the actuation forces and allows precise, gradual release of the prosthesis. A friction reducer tube may further be provided to facilitate withdrawing of the cover through an introducer sheath. The friction reducer tube is slidably disposed over the cover of the delivery catheter of the present invention, and includes a seal against the cover to provide hemostasis. The friction reducer tube is insertable within an introduction sheath, and allows movement of the delivery catheter with less friction than the introduction sheath, which must seal against a variety of invasive surgical devices. Optionally, a brace mechanically couples the proximal end of the shaft to the introduction sheath to prevent distal movement of the prosthesis or runners during deployment. Such a brace is particularly advantageous when a single surgeon is to manipulate the delivery catheter of the present invention.
The runners are again preferably formed of a high strength alloy. There are preferably between 1 and 20 runners, each runner being a strip which is longer than the prosthesis. The total width of all the runners is limited by the internal diameter of the cover, as the runners are usually affixed about the shaft side to side, and the runner/shaft assembly must slide within the cover. The runners will often be narrower than this, however, to allow the expanded prosthesis to anchor to the inner surface of the body lumen between the runners. The runners are each preferably in the range from 0.01 to 0.09 inch wide, and preferably between 0.001 and 0.02 inch thick.
In another aspect, the present invention provides an improved orientation indicating catheter for placement of an asymmetric prosthesis in a branching body lumen. The present orientation indicating catheter comprises an asymmetric marker, on the shaft structure which indicates the rotational orientation of the prosthesis. Preferably, a branch axial marker on the shaft structure indicates the axial location of the prosthesis branch. These rotational and axial indicators prevent placement of the prosthesis branch below the branching body lumen, or crossing of the branches, either of which could reduce or even completely block flow through one branch of the body lumen system. Similarly, a position indicating catheter having a safety marker prevents placement of a secondary prosthesis too far within the branch of a branching prosthesis, reducing the danger of the tubular prosthesis folding over and blocking flow.
In yet another aspect, the present invention provides an expandable tip catheter for placement of a radially compressible prosthesis having a large diameter portion and a small diameter end, the catheter comprising an elongate shaft structure having a prosthesis receptacle near a distal end, and a cover slidably disposed about the shaft structure. The cover comprises a body portion and a resilient structure extending from the distal end of the body portion. The catheter restrains the prosthesis with the small diameter end of the prosthesis in the distal resilient structure of the cover, allowing the distal end of the catheter to have a smaller outer diameter than the body. Advantageously, the distal end may be advanced into a smaller body lumen branch, and the expandable structure can expand over a large diameter end of the prosthesis as the cover is retracted into a larger body lumen. The resilient structure preferably comprises a braided mesh tubing with an elastomeric material disposed over the mesh tubing. Alternatively, the resilient structure comprises a sheath having one or more axial slits, or a rolled or folded pliable material.
According to the method of the present invention, a resilient, radially compressible prosthesis is loaded into a tubular cover by compressing the prosthesis between a plurality of elongate runners and sliding the runners into the cover. The cover may then be positioned within a body lumen so the prosthesis is at a target location, and deployed by withdrawing the cover relative to the prosthesis. Optionally, the runners exit the cover distally with the prosthesis, and are retracted after the cover. Alternatively, the runners and cover are retracted together.